Third, four grasses were evaluated as phytoremediation candidates via greenhouse experiments. The species were Agropyron spicata (bluebunch wheatgrass), A. cristatum (crested wheatgrass), Leymus cinerus (Great Basin wildrye), and Bromus tectorum (cheatgrass). Plant Cs concentrations were higher in Cs-spiked soil. Total Cs per seedling was greatest in the high Cs, high fertility, and high moisture soil treatment combination.

Invasion by non-native species is a serious ecological threat and the susceptibility of ecosystems to invasion is often highly correlated with soil resource availability. Understanding the role of plant-soil feedbacks in invaded ecosystems could provide insight into community successional trajectories following invasion and could improve our ability to manage these systems to restore native diversity. My dissertation examined how plant-soil feedbacks and resource availability influence the success of both cheatgrass and native species with three interrelated studies. In a large-scale observational study, I evaluated plant community characteristics as well as soil and plant nutrients associated with progressive cheatgrass invasion in a broadly distributed sagebrush ecological site type. I found that although many nutrient pools did not differ among levels of invasion, soil ammonium (NH4+) was negatively affected by increases in cheatgrass cover. Also, cheatgrass nutrient content did not differ across sites indicating that cheatgrass may alter plant available soil nutrients to the detriment of competitors while maintaining its own nutritional content via high nutrient use efficiency and/or soil mining. I also conducted a field experiment to provide a more mechanistic understanding of the role of disturbance on nutrient availability and invasion and to address potential management approaches. I evaluated the effects of 4-5 years of repeated burning, in combination with litter removal and post-fire seeding, on nutrient dynamics and plant responses. Results from my field experiment indicated that repeated burning is unlikely to decrease soil N availability in cheatgrass-dominated systems due to cool fire temperatures that do not volatilize biomass N and strong effects of weather on plant growth and soil processes. Repeated burning and litter removal, however, did have negative effects on litter biomass and C and N contents which negatively influenced cheatgrass biomass, density and reproduction. In addition, post-fire seeding with common wheat decreased cheatgrass abundance, likely due to competition. Integrated restoration approaches that decrease litter biomass and seed banks and increase competitive interactions may be more effective at reducing annual grasses and establishing desirable perennial species than approaches aimed at reducing soil nutrients. Together, the observational and experimental components of my dissertation indicate that plant-soil feedbacks in arid sagebrush shrublands are complex and that understanding these feedbacks requires both spatial and temporal variability in sampling. Furthermore, the results from these studies provide valuable information on techniques that could facilitate the restoration of cheatgrass-dominated systems to more diverse plant communities.

This book by soil scientists and ecologists reviews how and why plants influence soils. Topics include effects on mineral weathering, soil structure, and soil organic matter and nutrient dynamics, case studies of soil-plant interactions in specific biomes and of secondary chemicals influencing nutrient cycling, the rhizosphere, and potential evolutionary consequences of plant-induced soil changes. This is the first volume that specifically highlights the effects of plants on soils and their feedbacks to plants. By contrast, other texts on soil-plant relationships emphasize effects of soil fertility on plants, following the strongly agronomic character of most research in this area. The aspects discussed in this volume are crucial for understanding terrestrial ecosystems, biogeochemistry and soil genesis. The book is directed to terrestrial ecologists, foresters, soil scientists, environmental scientists and biogeochemists, and to students following specialist courses in these fields.

This book provides extensive and comprehensive knowledge to the researchers/academics who are working in the field of cesium contaminated sites, and the impact on plants. This book is also helpful for graduate and undergraduate students who are specializing in radioecology or safe disposal of radioactive waste, remediation of legacies and the impact on the environment. Radiocesium (137Cs and 134Cs) was released into the environment as a result of nuclear weapons testing in 1950s and 1960s (~1x1018 Bq), and later due to the Chernobyl accident in 1986 (8.5x1016 Bq) and Fukushima Daiichi Nuclear Power Plant in 2011 (~1x1017 Bq). 137Cs is still of relevance due to its half-life of 30 years. The study of radioisotope 137Cs is important, as production and emission rates are high compared to other radioisotopes, due to high fission yield and high volatility. This book contains original work and reviews on how cesium is released into the environment on translocation from soil to plants and further on to animals and into the human food chain. Separate chapters focus on the effective half-life of cesium in plants and on how different cultivars are responding in accumulation of cesium. Other key chapters focus on cesium impact on single cells to higher plants and also on remediation measures as well as on basic mechanism used for remedial options and analysis of transfer factors. The book rounds off by contributions on cesium uptake and translocation and its toxicity in plants after the Chernobyl and Fukushima accidents.

The objective of this research was to investigate vegetation and soil property structure in sagebrush steppe ecosystems as they recover from drastic disturbance, particularly in assessing the variability of properties across space. On reclaimed pipelines, I collected vegetation data and analyzed soil for organic carbon, total nitrogen, microbial community structure, moisture, salinity, and alkalinity. Using a Bayesian hierarchical mixed model, I quantified soil properties with posterior predictive distributions to compare reclaimed areas with the reference areas. The variance of most soil properties was affected by disturbance, and not always accompanied by a shift in the mean. Distributions for soil properties in reclaimed areas became more similar to those of undisturbed reference areas as recovery time increased. I then explored the differences in sampling designs, analysis, and inference gained from spatial and non-spatial soil data. I also conducted side-by-side analyses of each data type for a reclaimed area and an undisturbed area. The analysis of random data revealed differences in soil property averages between treatments. These differences were also apparent in the geostatistical analysis, which also provided information about the spatial structure in soil properties at the scale of individual plant effects (10 cm - 10 m). The third project expanded the assessment in both space and time, by including reclaimed pipelines that spanned 55 years, and by sampling at a scale up to 100 meters. I used Bayesian geostatistical models to quantify the correlation structure and to create surface predictions for measured properties. The reclaimed areas maintained uniform grass cover with low diversity and shrub establishment, while the responses of soil properties to disturbance and reclamation were variable. All three modeling approaches indicated that soil properties closely associated with vegetation experienced reduced variability and homogenization across space following disturbance. Soil abiotic properties appeared to be affected by the physical effects of disturbance, but were not associated with homogenization. Development of belowground heterogeneity was possibly delayed by the slow recovery of the plant community, particularly the shrub component. This research illustrates some long lasting ecological consequences of disturbance in sagebrush steppe and emphasizes the need for establishing shrubs in reclaimed sagebrush steppe.

The Jornada Basin LTER is located in the Chihuahuan Desert, the largest in North America. This region of south central New Mexico has a history of nearly 100 years as the basis for scientific research. This work gives a thorough, encompassing review of the tremendous array of observations resulting from experiments conducted in this ecosystem. Beginning with thorough descriptions of the most salient features of the region, the book then reviews a wide range of archived and active data sets on a diversity of biotic and abiotic features. It next presents a syntheses of important topics including livestock grazing and remediation efforts. A concluding chapter provides a synthesis of the principles that have emerged from this body of work, and how these relate to the broader fields of ecology and natural resource management. It concludes with recommendations for future research directions. The insightful views expressed in this volume should guide management of arid landscapes globally. This is the sixth volume in the Long Term Ecological Network Series.

Soils have been called the most complex microbial ecosystems on Earth. A single gram of soil can harbor millions of microbial cells and thousands of species. However, certain soil environments, such as those experiencing dramatic change exposing new initial soils or that are limited in precipitation, limit the number of species able to survive in these systems. In this respect, these environments offer unparalleled opportunities to uncover the factors that control the development and maintenance of complex microbial ecosystems. This book collects chapters that discuss the abiotic factors that structure arid and initial soil communities as well as the diversity and structure of the biological communities in these soils from viruses to plants.